Hypercholesterolemia induces leukocyte entrapment in the retinal microcirculation of rats

To evaluate leukocyte dynamics in the retinal microcirculation of hypercholesterolemic rats in vivo using acridine orange digital fluorography.

18 male pigmented rats were divided into 3 groups according to their diet; (A) control diet (0.1% cholesterol) for 8 weeks, (B) control diet for an initial 4 weeks followed by a high-cholesterol (HC) diet (5% cholesterol) for another 4 weeks and (C) HC diet for 8 weeks. Leukocyte dynamics were observed with acridine orange digital fluorography. The diameter of major retinal vessels and the number of leukocytes trapped in the retina were evaluated quantitatively.

Both groups B and C showed approximately 4-fold higher serum cholesterol levels than in group A. The diameters of retinal arteries and veins were not significantly different among the three groups. Also, no rolling leukocytes were observed in any of the groups. In the retinal microcirculation at 30 minutes after acridine orange injection, the density of trapped leukocytes in both groups B and C was significantly greater than in group A (23.19 +/- 2.13, 28.56 +/- 1.96 and 13.67 +/- 1.45 cells/mm(2), respectively, p < 0.01). Furthermore, group C exhibited a significantly greater number of trapped leukocytes than in group B (p < 0.01).

Enhanced leukocyte entrapment in the retinal microcirculation was induced in the early stage of hypercholesterolemia. Entrapment was increased as the period of hypercholesterolemia was prolonged. Leukocyte accumulation in the retina may be an early vascular dysfunction leading to arteriosclerosis in hypercholesterolemia.